1. Technical Field
One or more embodiments of the present invention generally relate to power management. In particular, certain embodiments relate to reducing the voltage supplied to a computing system component.
2. Discussion
As the trend toward advanced central processing units (CPUs) with more transistors and higher frequencies continues to grow, computer designers and manufacturers are often faced with corresponding increases in power and energy consumption. Furthermore, manufacturing technologies that provide faster and smaller components can at the same time result in increased leakage power. Particularly in mobile computing environments, increased power consumption can lead to overheating, which may negatively affect performance, and can significantly reduce battery life. Because batteries typically have a limited capacity, running the components of a mobile computing system may drain the capacity more quickly than desired.
Some modern mobile computing systems take into consideration the dynamic nature of computer applications in order to conserve battery capacity. For example, many computer applications cause the CPU to consume relatively high power at high performance for short periods of time, while requiring relatively low power operation the rest of the time (e.g., idle while waiting for user input). By limiting the high frequency and high voltage operation of the CPU to the time periods in which high performance is needed, the computing system can conserve a significant amount of power. For example, when the CPU anticipates being idle, the CPU can instruct the voltage regulator to drop the core voltage to a minimum operating voltage. Similarly, when the CPU is to be turned off, the core voltage can be further dropped to a minimum sustainable voltage that is programmed into the voltage regulator during the CPU manufacturing or board assembly process. The minimum sustainable voltage maintains the internal state of the CPU. Since active and leakage power are closely related to voltage, reducing the voltage can enable greater power savings, lower temperatures and longer battery life. While the above approach has been acceptable under certain circumstances, there still remains considerable room for improvement.
In particular, manufactured components tend to exhibit slightly different characteristics from one part to the next. For example, two CPU parts resulting from the same manufacturing process may have different minimum sustainable voltages. Conventional power management approaches, however, select a “worst case” minimum sustainable voltage for all CPUs of a given type and use this value to program the voltage regulator. Thus, a non-optimal minimum sustainable voltage is shared among all instances of a given computing system component. The same is true for other power saving parameters such as the minimum operating voltage. As a result, the majority of parts use non-optimal power saving parameters, which often results in missed power saving opportunities. Furthermore, conventional approaches do not permit the CPU to change the preset minimum value and therefore have limited ability to tailor the voltage regulator to individual components rather than a group of components.